Biomedical sensing and display apparatus

ABSTRACT

This disclosure describes a biomedical sensing and display apparatus wherein signals detected by a biomedical detecting means, such as electroencephalograph probes, are displayed on a suitable display means. In addition, the detected signals are converted from analog form into digital form and stored in a memory. Electrical system means are provided for comparing the stored signal with later detected signals and displaying the results of the comparison on a display means with the differences between the two signals being intensified. Further, electrical means are provided for applying active signals to some of the probes in order to invoke signals at other probes. In addition, an electroencephalograph probe housing wherein a plurality of probes are mounted in a semihemispherical structure is described. The housing houses microelectronic preamplifier means that are connected to the probes and includes a shielding means to prevent extraneous signals from disturbing the signals detected by the probes.

United States Patent [72] Inventor Robert L. Trent PrimaryExaminer-William E. Kamm 50 Front St., Marblehead, Mass. 01945Attorney-Griffin, Branigan and Kindness [21] Appl. No. 816,215 [22]Filed Apr. 15, 1969 45 patented No 30 197 ABSTRACT: This disclosuredescribes a biomedical sensing and display apparatus wherein signalsdetected by a biomedical detecting means, such as electroencephalographprobes, [54] BIOMEDICAL SENSING AND DISPLAY are displayed on a suitabledisplay means. In addition, the de- APPARATUS tected signals areconverted from analog form into digital l6Claims,3Drawing Figs. form andstored in a memory. Electrical system means are [52] U 8 Cl 128/2 1 Bprovided for comparing the stored signal with later detected ZB/DI'Gsignals and displaying the results of the comparison on a dis- [51 1 InA6) 6 play means with the differences between the two signals being [so]Fieid 128/2 06 B intensified. Further, electrical means are provided forapply- 2 06E R ing active signals to some of the probes in order toinvoke A 6 signals at other probes. In addition. anelectroencephalograph probe housin wherein a luralit of robes aremounted in a 8 P y P [55] References Cited semihemispherical structureis described. The housing houses UNITED STATES PATENTS microelectronicpreamplifier means that are connected to the probes and includes ashielding means to prevent extraneous fi f signals from disturbing thesignals detected by the probes. evine 3,411,495 ll/l968 Casby l28/2.l

I5 /3 II 1 2 63 gg qw CLOCK REAL TIME THZiS/gOLD CONTROL COUNTER 55CLOCK FROM SIGNAL INDICATORS 59 LEVEL 17 57 Como PROBE}; CONDITIONING 51CONTROL CO TROL AMPLIFIERS i glow 13% 158 SAMPLE a HOLD ("Sm/BumAMPLIFIERS 651 95 ACTIVE F5 69 SA L HOLD T0 PROBE ?5\ W/ii 77 25 PROBESCONTROL CHANNEL 73 0mm 97 MULTIPLEXER 4/0 CONVERTER 7:; DATA DATAPROCESSOR L 75 I with 3% CONTROL DIALS CONT 79 CHANNEL,MODE,TRIGGERCONTROL ME RY ACTIVE PROBE DISPLAY '99 W 4/ 93 RECORDER 29 55 f 27 8/ CA7/1005 VECTOR 43;

RA) TUBE GENERATOR 1 "YER/D ARRAY I 83 37 L 89 as LITE PEN 1 l 6/CONTROL PRIORITY 1 CONTROL INTERRUPTS FUNCTION KEYS 33 LEGEND. ANALOGSIGNALS PRINTER DIGITAL SIGNALS 1 BIOMEDICAL SENSING AND DISPLAYAPPARATUS The invention described herein was made by an employee of theUnited States Government and may be manufactured and used by or for thegovernment for governmental purposes without the payment of anyroyalties thereon or therefor.

BACKGROUND OF THE INVENTION Modern biomedical sensing and displayapparatus generally comprise an instrument connected to a plurality ofpatient-attached probes through a manually operated switch. The outputfrom the switch is connected to an amplifier or a plurality ofamplifiers, and the outputs from the amplifiers are connected to arecording device, such as a pen recorder. In this manner, the electricalsignals detected by the probes are monitored and recorded. The recordercan be a single-pen recorder or a multiple-pen recorder so that eitherthe signals detected by a single probe can be recorded or the signalsdetected by a plurality of probes can be simultaneously recorded. Therecord is later interpreted by skilled medical personnel to determinethe medical condition of the patient.

Instruments of the foregoing nature are well known for monitoring andrecording brain and heart signals. The former is known as anelectroencephalograph (EEG) while the later is known as anelectrocardiograph (EKG). While prior art instruments for monitoring andrecording medical signals have found widespread use, they have certaindisadvantages. For example, they merely monitor and record the signalsdetected by the probes. The recorded signals must later be analyzed byskilled medical personnel. Hence, these prior art systems requireskilled operators as well as skilled medical analysts. In addition, theydo not provide a means for comparing the signal detected by one probe atone time with signals detected by the same probe at a later time.Moreover, they provide no means for actively electrically stimulating apatient in the areas being probed.

Therefore, it is an object of this invention to provide a new andimproved biomedical sensing and display apparatus.

It is also an object of this invention to provide a biomedical sensingand display apparatus including means for comparing signals so thatdeviations can be detected between two sets of signals present at thesame location, either monitored at different times or subject todifferent physiological inputs which might cause variations in thesignal content.

It is another object of this invention to provide a biomedical sensingand display apparatus including means for applying electrical signals toone or more of a plurality of probes so as to evoke a response in otherprobes of said plurality of probes.

It is still another object of this invention to provide a new andimproved biomedical sensing and display apparatus including means forstoring one set of biomedical signals and means for comparing the storedsignals with a new set of biomedical signals, and including means fordisplaying deviations between the two sets of signals in an intensifiedmanner.

It will be appreciated by those skilled in the art that among prior artEEG system problems are the limited number of probes that can beattached to a patient and the difiiculties encountered in attaching theprobes and maintaining uniform contact resistance during theexamination. The attachment difficulty becomes increasingly moredifficult when it is desired to reattach a set of probes to the samepoints on a patient's head as they were previously attached in order toobtain comparison signals for comparing an old record with a new record.More specifically, prior art EEG apparatus is generally limited to aboutprobes per hemisphere. These probes must be individually spaced atdesired points on a patients head and attached to the head by a suitableadhesive. This procedure is both time consuming and tedious. In additionthe limited number of probes limits the number of cranial points thatcan be monitored. Further, this probe attachment procedure makes itextremely difiicult to obtain records from common probe points atdifferent periods of time for comparison purposes.

The prior art has attempted to solve the EEG probe problem in variousways. Various types of headgear for supporting the probes have beendeveloped. However, none of these approaches have entirely solved theproblem. For example, some of them merely support probes at a limitednumber of points. Others do not provide a suitable shielding means,hence, interferring signals are superimposed on the desired signals, anddetected by the probes, resulting in spurious and nonmeaningfulwavefonns in their recorded patterns.

Therefore, it is yet another object of this invention to provide a newand improved housing for supporting a plurality of electroencephalographprobes.

It is a still further object of this invention to provide a housingadapted to fit over the head of a patient for supporting a plurality ofelectroencephalograph probes that includes a suitable shielding meansfor preventing extraneous signals from being detected by the probes.

SUMMARY OF THE INVENTION In accordance with a principle of thisinvention, a biomedical sensing and display apparatus is provided.Biomedical signals from a plurality of probes are sequentially displayedon a display means. In addition, the signals are converted fromanalog-to-digital form and stored in a memory so that later sensedsignals can be compared with earlier stored signals. The results of thecomparison are displayed, with detailed deviations between the twocompared waveforms being intensified, if desired.

In accordance with another principle of this invention, electric meansare provided for applying active electric signals to some of the probesso as to evoke signals in other probes. The evoked biomedical signalsmay be recorded and/or compared with earlier evoked signals in a mannersimilar to the recording and/or comparison of nonevoked signals.

In accordance with still another principle of this invention, thresholdmeans are provided for setting thresholds for the signals detected bythe probes after amplification. If the thresholds are surpassed, asignal is generated which may be usedto notify the operator, interruptthe normal operation of the system, and, if desired, display saidwaveform and store the corresponding digital sampled information in thememory.

In accordance with still a further principle of this invention, asemihemispherical headpiece for supporting a plurality of EEG probes isprovided. The headpiece also houses plurality of microelectronicpreamplifiers which may be suitably connected to the probes. Moreover,the headpiece includes a shielding means for preventing external signalsfrom affecting the signals detected by the probes and amplified by themicroelectronic preamplifiers. Mechanical or electrical switching meansmay be provided to allow the individual probes to be used either as adetecting probe to sense EEG signals or as an active probe for applyingelectric signals to a patient so as to evoke EEG signals which would bedetected by other probes.

It will be appreciated by those skilled in the art and others that theinvention provides a new and improved biomedical apparatus which allowsboth monitoring of biomedical signals as well as comparing earlierobtained signals with later obtained signals. In this manner, deviationsfrom normal signals can be detected. The invention is useful withvarious types of biomedical problems. However, its greatest use is withprobes mounted so as to detect electrocardiograph signals,electroencephalograph signals and/or signals produced by otherelectrical transducers monitoring parameters associated with suchphysiological systems. The invention can be used for displaying andcomparing normally occurring biomedical signals or it can be used fordisplaying and comparing evoked biomedical signals. If desired, theinvention can apply an active electric signal to the. probes so as toevoke signals in other probes which are then displayed and/or compared.Alternatively, other external stimuli, such as lights, can be used toevoke biomedical signals in the probes as is well known in the priorart.

It will also be appreciated by those skilled in the art and others thatthe probe housing provided by the invention greatly improves EEGapparatus. Specifically, because the headgear for housing the probesgreatly increases the number of probes that can be applied to the headof a patient, any EEG apparatus is able to more accurately fix thelocation of lesions and tumors. In addition, the inclusion of a shieldimproves the signal-to-noise ratio of the overall system. Moreover,because the headgear has a predetermined array of probes, the same probepoints on a patients head can be easily reacquired after the housing hasbeen removed. Hence, skilled personnel are not required to reattachprobes to specific points on a patients head when a new EEG record is tobe made after a period of time has elapsed since a prior EEG record wasmade.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and many of theattendant advantages of this invention will become more readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when taken in conjunction with theaccompanying drawings wherein:

FIG. I is a block diagram of a preferred embodiment of the biomedicalsensing and display apparatus of the invention;

FIG. 2 is a pictorial diagram of an EEG probe housing formed inaccordance with the invention; and,

FIG. 3 is a side view of the EEG probe housing illustrated in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a preferredembodiment of a biomedical sensing and display apparatus formed inaccordance with the invention and comprises: a real-time clock 11; aprogram event counter 13; threshold limit indicators 15; a thresholdlimit distributor 17; signal conditioning amplifiers 19; sample and holdamplifiers 21; a channel multiplexer 23; an analogto-digital converter25; a hybrid array 27; a vector generator 29; a digital data processor31, including priority interrupts 33; an active probe control 35; and, aconsole 37. The console comprises: control dials 39; a display recorder31; a cathoderay tube 43; a lite pen 45; function keys 47', and, aprinter 49.

For ease of illustration analog signal paths are illustrated by thedouble lines in FIG. I and digital signal paths are illustrated by thesingle lines. In addition, while single interconnecting lines areillustrated between the various subsystems, it is to be understood thata plurality of connecting lines would be used in an actual embodiment ofthe invention to apply the required signals from one point to otherpoints.

The analog signals from the biomedical probes, which may beelectroencephalograph (EEG), electrocardiograph (EKG), or any othersuitable biomedical probes, are applied to the inputs of the signalconditioning amplifiers 19. That is, the analog output from each probeis separately connected to the input of one amplifier of the pluralityof amplifiers forming the signal conditioning amplifiers 19. The signalconditioning amplifiers amplify the input signals to voltage and/orcurrent levels suitable for application to the other subsystems of theinvention. The amplified analog outputs from the signal conditioningamplifiers 19 are applied via a suitable connecting wire(s) 51 to theinputs of the threshold limit indicators 15, the sample and holdamplifiers 21, and the channel multiplexer 23.

The real-time clock 1] generates clock pulses at any desired frequency,such as 100 kHz., for example. The clock pulses are applied via asuitable connector 53 to an input of the program event counter. Theprogram event counter counts the pulses generated by the real-time clock11 and applies control signals at suitable time intervals, via a controlwire(s) 55, to the digital data processor 31. In addition, the digitaldata processor may apply count control signals, via a control wire(s) 57to the program event counter. That is, the digital data processor inaccordance with the signals determined by the setting of the functionkeys 47, applies control signals to the program event counter 13 whichsignals determine the number of clock pulses that must be counted beforea predetermined control signal is applied via the control wire(s) 55 tothe digital data processor 31. When a control signal is applied to thedigital data processor 31 by the program event counter, the digital dataprocessor generates various control types of signals and applies them inthe manner hereinafter described.

The digital data processor 31 is connected via a suitable controlwire(s) 58 to the threshold limit distributor 17. And, the thresholdlimit distributor 17 is connected via a level control wire(s) 59 to thethreshold limit indicators 15. The threshold limit distributordetermines which probes are to be connected to the threshold limitindicators and sets the threshold limits for those channels. Probedetermination and threshold limits are determined and set in accordancewith control signals from the digital data processor which signals aredetermined by the action of the function keys 47. That is, the functionkeys 47 control the overall operation of the system in the manner hereindescribed. More specifically, when the function keys are depressed, thedigital data processor 31 receives signals via a wire(s) 61 at itspriority interrupt section 33. The digital data processor interprets thefunction key signals and applies control signals to the varioussubsystems of the invention. Included in the control signals arethreshold signals which are applied via control wire(s) 58 to thethreshold limit distributor I7.

When the threshold limit indicators detect that a particular probesignal has surpassed a particular threshold, a control signal is appliedby the threshold limit indicators via a control wire(s) 63 to theprogram event counter 13 and via a sense wire(s) 65 to the digital dataprocessor 3i. The control signal from the threshold limit indicators onwire(s) 63 disables the program event counter 13 from counting furtherpulses and, the sense signal on wire( s) 65 causes a priority interruptwhich interrupts the normal operation of the digital data processor. Inaddition to the foregoing operations, the threshold limit indicator alsoapplies a control signal when necessary via a com trol wire(s) 67 to thesample and hold amplifiers 21 which disables the operation of the sampleand hold amplifiers.

The sample and hold amplifiers 21 are formed of any several well-knownamplifier circuits which sample signals and maintain or hold a record ofthe sampled signals for a predetermined time. The rate of sampling andtime of holding being determined by a control signal applied to thesample and hold amplifiers by the digital data processor via a sampleand hold control wire(s) 69. When and if desired, the sample and holdamplifiers apply their sampled and hold analog signals to the channelmultiplexer via a signal wire(s) 71.

The output from the channel multiplexer 23 is applied via a signalwire(s) 73 to the input of the analog-to-digital converter 25. Thedigital output of the analog-to-digital converter 25 is applied to thedigital data processor 31 via a digital data wire(s) 74. In the digitaldata processor, the digital data signal is applied to the memory in anyof many well-known manners. To control the operation of the channelmultiplexer, the digital data processor applies a channel, mode andtrigger control signal to the channel multiplexer 23 via a channel, modeand trigger control wire(s) 75. This control signal determines thechannel mode of operation of the multiplexer (i.e., rate and sequence ofswitching from one channel to the next channel) and when each channel sanalog-to-digital conversion is to be started (triggered). In accordancewith the trigger signal, the channel multiplexer applies a convertcontrol signal to the analog-to-digital converter 25 via a convertcontrol wire(s) 77. In general, this signal starts and maintains theanalog-todigital conversion for a particular probe signal.

Which channel or channels (the number of channels being determined bythe number of analog inputs applied to the channel multiplexer from itsvarious sources) of the channel multiplexer 23 are to have their signalsconverted in sequence by the analog-to-digital converter is determinedby the adjustment of control dials 37. That is, the control dialsdetermine which channels are to be read and convened by applyingsuitable control signals via a control wire(s) 79 to the channelmultiplexer 23.

The hybrid array 27 is connected to the digital data processor 31 via ameans of connection illustrated as two wires 81 and 83. One wire(s) 81carries the digital signal applied by the analog-to-digital converter tothe digital data processor 31 either by reading from memory or directlyfrom the analog-todigital converter. This digital signal includeshorizontal, vertical and intensity information about the original analogsignal. The other wire(s) 83 carries a digital signal that includeshorizontal, vertical and intensity modifying information. The hybridarray in a well-known manner receives these digital signals andgenerates an analog output signal in accordance therewith. Hence, thehybrid array acts as a digital-to-analog converter that reconstructs orreconstitutes the original analog signal. In addition, the hybrid arraycan modify the original analog signal. The output from the hybrid arrayis, hence, an analog signal that includes horizontal, vertical andintensity information, modified or unmodified, as desired.

The output from the hybrid array is applied via signal wire(s) 85 to thechannel multiplexer 23 and via a signal wire(s) 87 to the vectorgenerator 29. The vector generator also receives a control signal, via acontrol wire(s) 89, from the priority interrupt portion 33 of thedigital data processor 31. The vector generator converts the hybridoutput signals into horizontal, vertical and intensity informationsignals suitable for application to a cathode-ray tube or a displayrecorder. Consequently, these signals are applied to the cathode-raytube 43 via a signal wire(s) 91 and to the display recorder 41 via asignal wire(s) 93.

The active probe control 35 is adapted to apply electrical signals toany of the biomedical probes connected to the patient. A switchingcontrol signal is connected via a control wire(s) 95 to a switchingmeans (not shown) to control the application of an analog signal appliedvia an analog signal wire(s) 97 to one or more of the plurality ofprobes. In addition, the switching control signal causes a disconnectionof the signal applying probes from input of the signal conditioningamplifiers 19. The operation of the active probe control 35 iscontrolled by a control signal from the digital data processor 31applied to it via a wire(s) 99. The function keys 47 determine thenature of the control signal, that is, the function keys control thedigital data processor 31 so that it applies a suitable control signalalong the control wire(s) 99 to the active probe control 35. lnaccordance with this signal, the active probe control applies aswitching control signal to wire(s) 95 and an electrical active signalto wire(s) 97. In this manner, one or more of the probes applies anactive electrical signal to one or more points on the patient. Thissignal evokes a response from the patient which is sensed by theremaining probes.

The foregoing description has described the basic connections of theinvention and the functions of the various subsystems contained therein.So that the invention is more clearly understood, the followingdescription of the overall operation of the invention is presented.

Because of the aperiodic character of the individual signals beingmonitored by the invention, the analog signal sampling rate must beconsiderably higher than that formulated by the Nyquist samplingtheorem; particularly, if a detailed study and comparison of portions ofthe aperiodic signals represents a major consideration. This inventionis flexible in order to monitor on command, any number of channels at anindividual sampling rate up to a maximum figure, such as 100 kHz., forexample, wherein, the number of channels times the sampling rate equalsthe maximum figure. Thus, one channel could be sampled at 100 kHz. or 50channels could be sampled at 2 kHz. In between, the sampling rate variesin accordance with the number of channels being sampled. In this manner,the very rapid sampling of a particular channel or limited number ofchannels can be provided, if desired.

It is assumed in the following description that the system has just beenplaced in operation and that no equivalent analog signal in digital formhas been stored in the memory. The signal flow path for one analogsignal of a plurality of signals being simultaneously monitored isdescribed. For purposes of description, it is assumed that the totalnumber of analog signals being monitored is 20 so that the sampling rateis 5 kHz.

Upon initiation of operation, the analog signals appearing at the outputof the signal conditioning amplifiers 19 are simultaneously impressedupon the inputs of the threshold limit indicators 15, the sample andhold amplifiers 21, and the channel multiplexer 23. Previously, theanalog-to-digital converter 25, and the memory portion of the digitaldata processor have been enabled. More specifically, the function keys(which may be operated by a digital program if desired) provide acontrol signal along control wire(s) 61 to the digital data processorwhich in turn generates control signals that enable the subsystems. Thecathode-ray tube 43 and the display recorder 41 on the console 37 areenabled by suitable enabling switches.

The individual analog waveforms appearing at the input of the channelmultiplexer 23 are each sampled every 200 microseconds (5 kHz. rate).Each sample or waveform section is converted by the analog-to-digitalconverter 25 into a digital signal corresponding to the amplitude ofthese sampled sections. This digital information is available to thememory of the digital data processor 31. In addition, it is applied tothe hybrid array 27 via wire(s) 81. The hybrid array reconstitutes thisinformation in analog form and applies it to the vector generator 29.The vector generator applies the reconstituted analog signal to thecathode-ray tube 43 and the display recorder 41 where it is displayed.

The operator of the invention, after ascertaining that the waveforms aredisplayed with clarity and sufficient detail, and represent informationthat is required and relevant (in terms of biomedical information)operates a suitable function key which causes the channel multiplexer tosense the output from the hybrid array 27 and apply it via theanalog-to-digital converter to the digital data processor wherein it isstored in the memory. In this manner, the analog signals received at allof the probes are viewed by the operator of the system and stored in thememory portion of the digital data processor.

For the purposes of the following description, it is assumed thateither: (a) some time has passed, and it is desired to assess progressin the clinical condition of the patient; or, (b) that some action hastaken place which is believed to have an effect on the clinicalcondition of the patient. The action causing the effect may come fromvarious sources, such as the in troduction of medication, exercise, anevoked potential instituting means (i.e., light, heat, blinking of eyes,moving members of the body, etc. or active signals (i.e., introductionof an active electric signal to some of the probes, introduction of apacemaker, etc. for example.

Regardless of the cause, it is now desired to remonitor the probesignals and observe the differences, if any, that have occurred in theirwaveforms. in some cases, it may be desirable to monitor the signals atsome fixed time after the introduction of the action causing thewaveforms to be modified. If so, this time delay is introduced into thesystem by means of the fu nction keys andthe control dials. in addition,as a result of previous experience, it is often desirable to set upthreshold limits for the detection of theoretically meaningfulmodifications (either amplitude or phase) occurring in portions of thewaveforms. These threshold limits are set up by an appropriateadjustment of the function keys in the manner heretofore described. Thatis, as previously described, the function keys through the digital dataprocessor control the threshold limit distributor. And, the thresholdlimit distributor controls the setting of threshold limits in thethreshold limit indicators 15.

After the system has been set up as described in the precedingparagraphs, it operates automatically to resample the analog signalsfrom all probes of interest and display the new waveforms on thecathode-ray tube 43. If the interest in the signal is such that it isconcentrated on transient phenomena which are expected to occur at somefixed period of time after an action creating signal has been impressed,the control dials 39 control the channel multiplexer to read the analogsignal information after the period of time has passed. If desired, thissignal can be reconstituted in the manner previously described andapplied to the cathode-ray tube 43. Alternatively, it can be directlyapplied to the memory.

If it is desired to perform a comparison between a stored signal from aparticular probe and a new signal, the digital data processor reads outboth signals from its memory and compares them in any of severalwell-known manners. The results of the comparison are reconstituted anddisplayed on the cathode-ray tube. If it is assumed that the new analogsignal differs from the old" or stored analog signal, the signaldisplayed on the cathode-ray tube is a faithful replica of the newanalog signal with differences in the waveform characteristicsintensified. That is, as previously described, the hybrid array and thevector generator operate so that the displayed signal is intensitymodulated where differences in the waveform characteristics occur.

If desired, both of the new analog signals can be stored in memorywithout losing the previously stored signals by suitably operating thefunction keys. Thus, later comparison and study of the waveforms can beperformed by a competent individual. The limiting factor being, ofcourse, the size of the memory provided by the overall system. Inaddition, if desired, at any time the operator of the invention can readout a signal from memory and have it reconstituted and displayed on thecathode-ray tube or the display recorder. Moreover, if desired,displayed signals can be printed out as hard copies by the printer 49.Finally, the cathode ray tube could be a plurality of cathode-ray tubesso that a plurality of probe signals can be simultaneously displayed.Alternatively, the cathode-ray tube could be a plural beam cathode-raytube.

It will be appreciated from the foregoing description that the inventionprovides a novel biomedical apparatus for sensing and displayingbiomedical signals. In addition, the system provides means for comparinga previously stored biomedical signal with a later received biomedicalsignal. The results of the comparison are intensity modulated at pointsin the waveform where a difference between the two signals occurs sothat differences can be easily observed. In addition to providing asystem for displaying and comparing bio-medical signals, the inventionalso includes a novel system for mounting a plurality of probes suitablefor obtaining electroencephalograph waveforms. This apparatus isillustrated in FIGS. 2 and 3 and hereinafter described.

The EEG probe housing apparatus illustrated in FIGS. 2 and 3 is theshape of a semihemisphere or helmet formed of two half-hemisphericalsections 101 and 103. The half-hemispherical sections I01 and 103 aremirror images of one another and are adapted to fit over the upperportion of the patients head, one being located on one side of the headand the other being located on the other side of the head.

Each half-hemispherical section comprises an inner support member 105. Aplurality of adjustable cushion spacers 107 pass through each innersupport member 105. For purposes of clarity, only two of the adjustablecushion spacers 107 are illustrated in FIGS. 2 and 3, however, as manyas necessary may be included. The adjustable cushion spacers 107 may bethreaded into the inner support members 105 or held in any othersuitable manner that allows inward and outward movement. Also passingthrough the inner support members 105 are a plurality of probes 109. Theprobes are also adapted to move inwardly and outwardly by any suitablemeans, such as being threaded through the inner support member 105. Aplurality of mechanical springs 11] are connected between the two innersupport members 105 so as to cause an inwardly acting force at the lowerends of the support members. That is, the springs are connected across afront-rear gap between the sections so as to force the two sectionstoward one another. Hence, when a patients head is placed inside of thehousing, the housing is firmly affixed to the head.

Located outside of the inner support member of section 101 and 103 andformed similar thereto is a protective overlay 113 incorporating afaraday shield. The adjustable cushion spacers 107 and the probes 109pass through the faraday shield so that they can be easily movedinwardly and outwardly as desired. Located between the faraday shields113 and the inner support members 105 are a plurality of microelectronicpreamplifiers 115. The inputs of the microelectronic preamplifiers arenormally connected to the probes. The outputs of the microelectronicpreamplifiers are connected to a male connector 117 located at the backof each of the inner support members 105 as illustrated in FIG. 3. Afemale connector 119 connected to a cable 121 is adapted to be attachedto the male connector 117. The female connector is connected to theinputs of the signal conditioning amplifiers l9 and the outputs of theactive probe control 35 illustrated in FIG. I.

It will be appreciated from the foregoing description that the housingillustrated in FIGS. 2 and 3 and forming a portion of the invention isrelatively uncomplicated. In addition, it allows the probes to bearrayed in a predetermined array format as illustrated by the dashedlines in FIG. 3. Moreover, a considerably larger number of probes can beapplied to the head of a patient than can be applied by prior art probehousing apparatus. Further, because microelectric preamplifiers arelocated near the probes lower level signals than could be detected byprior art devices can be detected. Finally, because a faraday shield isprovided, extraneous signals are prevented from having an undesirableeffect on the signals sensed by the probes, thereby improving thesignal-to-noise ratio of each input signal.

The embodiments of the invention in which an exclusive property orprivileges are claimed are defined as follows:

1. A biomedical sensing and display apparatus comprising:

a plurality of biomedical probes, suitable for attachment to a livingbody, for detecting signals generated by the living body and applyingsignals to the living body;

a channel multiplexer connected to receive biomedical signals from saidplurality of biomedical probes and for applying the biomedical signalssequentially to an output terminal;

an analog-to-digital converter connected to the output terminal of saidchannel multiplexer for converting the biomedical signals at the outputterminal of said channel multiplexer from analog form to digital form;

a digital data processor including a memory connected to the output ofsaid analog-to-digital converter for storing said digital signals insaid memory;

reconstitution means connected to said digital data processor forreconstituting signals stored in the memory of said digital dataprocessor for digital form to analog form;

display means connected to said reconstitution means for displaying saidreconstituted analog signals;

said digital data processor also including means for reading out signalsstored in said memory and for comparing said signals, the results ofsaid comparison being applied to said reconstitution means to modify thedisplay signal also applied to said reconstitution means;

control means connected to said digital data processor for controllingthe operation of said digital data processor, said digital dataprocessor also being connected to said channel multiplexer and to saidreconstitution means for controlling the operation of said channelmultiplexer and said reconstitution means;

threshold limit indicators connected to receive said biomedical signalsfrom said plurality of biomedical probes; and,

a threshold limit distributor connected to said digital data processorand to said threshold limit indicators for receiving control signalsfrom said digital data processor and for applying threshold levelcontrol signals to said threshold limit indicators.

2. A biomedical sensing and display apparatus as claimed in claim 1including sample and hold amplifiers connected to receive saidbiomedical signals from a plurality of probes, the output of said sampleand hold amplifiers is connected to said channel multiplexer, saidsample and hold amplifiers also connected so as to receive sample andhold control signals from said digital data processor.

3. A biomedical sensing and display apparatus as claimed in claim 2including a real-time clock for generating clock pulses at apredetermined frequency and a program event counter connected to saidreal-time clock to count said clock pulses, said program event counterconnected to said digital data processor to apply control signals tosaid digital data processor and to receive control signals from saiddigital data processor.

4. A biomedical sensing and display apparatus as claimed in claim 3including an active probe control connected to apply active electricalsignals to said plurality of probes.

5. A biomedical sensing and display apparatus as claimed in claim 3including signal conditioning amplifiers connected to receive saidbiomedical signals from said plurality of probes and to apply saidsignals to said threshold limit indicators, said sample and holdamplifiers and said channel multiplexer.

6. A biomedical sensing and display apparatus as claimed in claim 5including control dials connected to said channel multiplexer todetermine which probe signals of said plurality of probe signals are tobe applied to said analog-to-digital converter; and wherein said controlmeans includes function keys connected to said digital data processor tocontrol the operation of said digital data processor.

7. A biomedical sensing and display apparatus as claimed in claim 6wherein said reconstitution means includes a hybrid array connected tosaid digital data processor and a vector generator, said vectorgenerator connected to the output of said hybrid array and to the inputof said display means.

8. A biomedical sensing and display apparatus as claimed in claim 7wherein said display means includes a cathode-ray tube.

9. A biomedical sensing and display apparatus as claimed in claim 8wherein said threshold limit indicators are connected to apply a controlsignal to said program event counter and said sample and hold amplifierswhen a predetermined threshold has been surpassed and, to said digitaldata processor to apply a sense signal to said digital data processorwhen said predetermined threshold has been surpassed.

10. A biomedical sensing and display apparatus as claimed in claim 9wherein said digital processor includes means for reading out signalsstored in its memory and for comparing said signals, the results of saidcomparison being applied to said hybrid array to modify the displaysignal also applied to said hybrid array.

11. A biomedical sensing and display apparatus as claimed in claim 10wherein each of said plurality of biomedical probes is anelectroencephalographic probe; and, further including anelectroencephalographic probe housing suitable for supportingelectroencephalographic probes adjacent to the head of a patient, saidelectroencephalographic probe housing being formed of two sectionsattached to one another, each ofsections comprising:

an inner support member that is halfhemispherical in shape, said innersupport member including a plurality of apertures formed between thesurfaces thereof and arranged in a predetermined array, said pluralityof electroencephalographic probes being mounted in said apertures in aninwardly and outwardly movable manner;

spacing means attached to said inner support member for maintaining saidinner support member a predetermined distance from the head of saidpatient; and,

electrical shielding means fonned similar to said inner support memberand mounted about the outer surface of said inner support member inspaced relationship thereto so as to electrically shield said pluralityof electroencephalographic probes from extemal electrical signals. 12.biomedical sensing and display apparatus as claimed in claim 11 whereinsaid inner support members of said two sections are attached together bysprings that tend to force one of said inner support members toward theother of said inner support members.

13. A biomedical sensing apparatus as claimed in claim 12 wherein saidspacing means includes adjustable cushioned spacers moveably mountedthrough apertures in said inner support members.

14. A biomedical sensing and display apparatus as claimed in claim 13including:

a plurality of microelectronic preamplifiers mounted between said innersupport members and said electrical shielding means, the inputs of oneof said plurality of microelectronic preamplifiers being connected toeach of said electroencephalographic probes; and,

a connector attached to said sections and electrically connected to theoutputs of said microelectronic preamplifiers and to the inputs of saidsignal conditioning amplifiers.

15. An electroencephalographic probe housing suitable for supportingelectroencephalographic probes adjacent to the head of a patient, saidelectroencephalographic probe housing comprising:

two sections, each of said sections comprising:

an inner support member that is half-hemispherical in shape and includesa plurality of apertures formed between the surfaces thereof andarranged in a predetermined array;

a plurality of electroencephalographic probes, one of said probes beingmounted in each of said plurality of apertures in said inner supportmember, said plurality of electroencephalographic probes being mountedso as to be movable inwardly and outwardly;

spacing means attached to said inner support member for maintaining saidinner support member a predetermined distance from the head of saidpatient, said spacing means comprising a plurality of threaded shaftshaving cushions on their inner ends, said threaded shafts passingthrough threaded apertures in said inner support member; and,

electrical shielding means formed similar to said inner support memberand mounted outside of said inner support member in spaced relationshipthereto so as to electrically shield said plurality ofelectroencephalographic probes from external electrical signals; and,

springs attached to said inner support members for biasing one sectionof said two sections towards the other section of said two sections.

16. An electroencephalographic probe housing as claimed in claim 15including:

a plurality of microelectronic preamplifiers mounted between said innersupport members and said electrical shielding means, the inputs of oneof said plurality of microelectronic amplifiers being connected to eachof said electroencephalographic probes; and,

a connector attached to said sections and electrically connected to theoutputs of said plurality of microelectronic preamplifiers.

i k 0 l i

1. A biomedical sensing and display apparatus comprising: a plurality ofbiomedical probes, suitable for attachment to a living body, fordetecting signals generated by the living body and applying signals tothe living body; a channel multiplexer connected to receive biomedicalsignals from said plurality of biomedical probes and for applying thebiomedical signals sequentially to an output terminal; ananalog-to-digital converter connected to the output terminal of saidchannel multiplexer for converting the biomedical signals at the outputterminal of said channel multiplexer from analog form to digital form; adigital data processor including a memory connected to the output ofsaid analog-to-digital converter for storing said digital signals insaid memory; reconstitution means connected to said digital dataprocessor for reconstituting signals stored in the memory of saiddigital data processor for digital form to analog form; display meansconnected to said reconstitution means for displaying said reconstitutedanalog signals; said digital data processor also including means forreading out signals stored in said memory and for comparing saidsignals, the results of said comparison being applied to saidreconstitution means to modify the display signal also applied to saidreconstitution means; control means connected to said digital dataprocessor for controlling the operation of said digital data processor,said digital data processor also being connected to said channelmultiplexer and to said reconstitution means for controlling theoperation of said channel multiplexer and said reconstitution means;threshold limit indicators connected to receive said biomedical signalsfrom said plurality of biomedical probes; and, a threshold limitdistributor connected to said digital data processor and to saidthreshold limit indicators for receiving control signals from saiddigital data processor and for applying threshold level control signalsto said threshold limit indicators.
 2. A biomedical sensing and displayapparatus as claimed in claim 1 including sample and hold amplifiersconnected to receive said biomedical signals from a plurality of probes,the output of said sample and hold amplifiers is connected to saidchannel multiplexer, said sample and hold amplifiers also connected soas to receive sample and hold control signals from said digital dataprocessor.
 3. A biomedical sensing and display apparatus as claimed inclaim 2 including a real-time clock for generating clock pulses at apredetermined frequency and a program event counter connected to saidreal-time clock to count said clock pulses, said program event counterconnected to said digital data prOcessor to apply control signals tosaid digital data processor and to receive control signals from saiddigital data processor.
 4. A biomedical sensing and display apparatus asclaimed in claim 3 including an active probe control connected to applyactive electrical signals to said plurality of probes.
 5. A biomedicalsensing and display apparatus as claimed in claim 3 including signalconditioning amplifiers connected to receive said biomedical signalsfrom said plurality of probes and to apply said signals to saidthreshold limit indicators, said sample and hold amplifiers and saidchannel multiplexer.
 6. A biomedical sensing and display apparatus asclaimed in claim 5 including control dials connected to said channelmultiplexer to determine which probe signals of said plurality of probesignals are to be applied to said analog-to-digital converter; andwherein said control means includes function keys connected to saiddigital data processor to control the operation of said digital dataprocessor.
 7. A biomedical sensing and display apparatus as claimed inclaim 6 wherein said reconstitution means includes a hybrid arrayconnected to said digital data processor and a vector generator, saidvector generator connected to the output of said hybrid array and to theinput of said display means.
 8. A biomedical sensing and displayapparatus as claimed in claim 7 wherein said display means includes acathode-ray tube.
 9. A biomedical sensing and display apparatus asclaimed in claim 8 wherein said threshold limit indicators are connectedto apply a control signal to said program event counter and said sampleand hold amplifiers when a predetermined threshold has been surpassedand, to said digital data processor to apply a sense signal to saiddigital data processor when said predetermined threshold has beensurpassed.
 10. A biomedical sensing and display apparatus as claimed inclaim 9 wherein said digital processor includes means for reading outsignals stored in its memory and for comparing said signals, the resultsof said comparison being applied to said hybrid array to modify thedisplay signal also applied to said hybrid array.
 11. A biomedicalsensing and display apparatus as claimed in claim 10 wherein each ofsaid plurality of biomedical probes is an electroencephalographic probe;and, further including an electroencephalographic probe housing suitablefor supporting electroencephalographic probes adjacent to the head of apatient, said electroencephalographic probe housing being formed of twosections attached to one another, each of sections comprising: an innersupport member that is half-hemispherical in shape, said inner supportmember including a plurality of apertures formed between the surfacesthereof and arranged in a predetermined array, said plurality ofelectroencephalographic probes being mounted in said apertures in aninwardly and outwardly movable manner; spacing means attached to saidinner support member for maintaining said inner support member apredetermined distance from the head of said patient; and, electricalshielding means formed similar to said inner support member and mountedabout the outer surface of said inner support member in spacedrelationship thereto so as to electrically shield said plurality ofelectroencephalographic probes from external electrical signals.
 12. Abiomedical sensing and display apparatus as claimed in claim 11 whereinsaid inner support members of said two sections are attached together bysprings that tend to force one of said inner support members toward theother of said inner support members.
 13. A biomedical sensing apparatusas claimed in claim 12 wherein said spacing means includes adjustablecushioned spacers moveably mounted through apertures in said innersupport members.
 14. A biomedical sensing and display apparatus asclaimed in claim 13 including: a plurality of microelectronicpreamplifiers mounted between said inner support members and saidelectricaL shielding means, the inputs of one of said plurality ofmicroelectronic preamplifiers being connected to each of saidelectroencephalographic probes; and, a connector attached to saidsections and electrically connected to the outputs of saidmicroelectronic preamplifiers and to the inputs of said signalconditioning amplifiers.
 15. An electroencephalographic probe housingsuitable for supporting electroencephalographic probes adjacent to thehead of a patient, said electroencephalographic probe housingcomprising: two sections, each of said sections comprising: an innersupport member that is half-hemispherical in shape and includes aplurality of apertures formed between the surfaces thereof and arrangedin a predetermined array; a plurality of electroencephalographic probes,one of said probes being mounted in each of said plurality of aperturesin said inner support member, said plurality of electroencephalographicprobes being mounted so as to be movable inwardly and outwardly; spacingmeans attached to said inner support member for maintaining said innersupport member a predetermined distance from the head of said patient,said spacing means comprising a plurality of threaded shafts havingcushions on their inner ends, said threaded shafts passing throughthreaded apertures in said inner support member; and, electricalshielding means formed similar to said inner support member and mountedoutside of said inner support member in spaced relationship thereto soas to electrically shield said plurality of electroencephalographicprobes from external electrical signals; and, springs attached to saidinner support members for biasing one section of said two sectionstowards the other section of said two sections.
 16. Anelectroencephalographic probe housing as claimed in claim 15 including:a plurality of microelectronic preamplifiers mounted between said innersupport members and said electrical shielding means, the inputs of oneof said plurality of microelectronic amplifiers being connected to eachof said electroencephalographic probes; and, a connector attached tosaid sections and electrically connected to the outputs of saidplurality of microelectronic preamplifiers.